Adding JSON Objects to JSON Array

Question

For example, if I make something like this:

<?php
//first json object
$cars[] = "1";
$cars[] = "2";
$cars[] = "3";
$cars[] = "4";
//second json object
$cars[] = "22";
$cars[] = "33";
$cars[] = "44";
$cars[] = "55";
//now i need to add them to the json array "cars"
echo json_encode(array("cars" => $cars));

?>

The output will become :

{"cars":["1","2","3","4"]}

However, I want it to be:

     {
    "cars": [
        {"1", "2", "3", "4"},
        {"22", "33", "44", "55"}
    ]
     }

EDIT (editing my old questions):

First of all, the result i wanted is not a valid JSON.

It has to be something like this:

  {
    "cars": [
        ["1", "2", "3", "4"],
        ["22", "33", "44", "55"]
    ]
 }

In order to get the above result, simply do the following:

The entire code:

<?php
// Add the first car to the array "cars":
$car = array("1","2","3","4");
$cars[] = $car;
// Add the second car to the array "cars":
$car = array("22","33","44","55");
$cars[] = $car;
//Finally encode using json_encode()
echo json_encode(array("cars" => $cars));
?>

Answer 1

Here's the closest you can get with valid JSON:

$cars[] = array("1","2","3","4");
$cars[] = array("22","33","44","55");

echo json_encode(array("cars" => $cars));

//{"cars":[["1","2","3","4"],["22","33","44","55"]]}

$cars[] = (object) array("1","2","3","4");
$cars[] = (object) array("22","33","44","55");

echo json_encode(array("cars" => $cars));

//{"cars":[{"0":"1","1":"2","2":"3","3":"4"},{"0":"22","1":"33","2":"44","3":"55"}]}

Answer 2

In JSON [] is an indexed array, eg: array(1,2,3)

and {} is an associative array, eg: array('one'=>1, 'two'=>2, 'three'=>3)

The syntax you've specified in your example is invalid. The closest you're going to get is:

echo json_encode(array(
  'cars'=>array(
    array(1,2,3,4),
    array(11,22,33,44)
  )
));

//output: {"cars":[[1,2,3,4],[11,22,33,44]]}